When inspecting a tire's appearance, an inspector inspects outer side surfaces (outer surfaces) and inner side surfaces (inner surfaces) of all tires on the basis of a tactile sensation when touching the surfaces by hand as well as visually. For such an inspection of a tire inner surface, various methods and devices have been proposed for carrying out the inspection automatically using cameras, laser displacement gauges, or the like to measure the luminance, shape, and the like of the tire inner surface without making contact therewith.
For example, a tire inspection device disclosed in Japanese Unexamined Utility Model Registration Application Publication No. 1987-016450 inspects the position and depth of a separation in a tire inner surface through dual-exposure holographic interferometry using a laser. This configuration efficiently and clearly detects a separation in a tire, which not only contributes to quality control for tires but also ensures that retreading processes can be carried out precisely.
A tire inspection device disclosed in Japanese Unexamined Patent Application Publication No. 2012-112838 includes an inspection unit including an illumination unit, a camera, and a reflective mirror curving along an inner circumferential surface of a tire, and a drive unit that rotates the tire and the inspection unit relative to each other around an axis of the tire. With this inspection device, a photographing unit captures light from the inner circumferential surface of the tire, the light being reflected by the mirror, while rotating the tire and the inspection unit relative to each other. This allows an upper half part and a lower half part of the tire in a tire width direction to be simultaneously imaged by two imaging units.
A tire testing device disclosed in Japanese Unexamined Patent Application Publication No. 2008-203258 includes a measurement unit including at least three measurement heads, and each of the measurement heads has an illumination member and a shearing member. The first and second measurement heads scan an outer side surface of a tire's side wall. The third measurement head scans at least an inner side surface of a tread area. The use of this device enables a tire to be tested quickly and fully.
An appearance/shape inspection device for an inspection subject disclosed in Japanese Unexamined Patent Application Publication No. 2003-240521 images a tire placed on a rotating table while rotating the tire, using a light projection means that illuminates white slit light and a color charge-coupled-device (CCD) camera that images an area irradiated with the slit light. Furthermore, coordinates and luminance of the tire are detected from image data obtained by a coordinate calculating means and a luminance calculating means. Three-dimensional coordinate data and a color image of the tire are reconstructed from obtained shape data and luminance data of the tire.
An appearance and shape inspection device for an inspection subject disclosed in Japanese Unexamined Patent Application Publication No. 2001-249012 obtains appearance data generated by a first imaging means imaging a line area formed by irradiating a tire, which is an inspection subject, with first slit light, and obtains shape data generated by a second imaging means imaging the same line area at a predetermined angle of tilt, by using second slit light with which the line area is irradiated. Furthermore, the quality of the appearance is determined from the appearance data, and the quality of the shape is determined from the shape data.
An article inspection method disclosed in Japanese Unexamined Patent Application Publication No. 2009-115512 determines the quality of an appearance on the basis of image data generated with a rotating table that holds a tire, an irradiation means that irradiates a tire inner surface with a line-form laser beam, and a camera that is attached to a robot hand and images the tire inner surface.
However, problems with mechanisms that measure the inner side of a tire includes the space in a tire inner side, corresponding to a tire cavity region filled with air when the tire is assembled on a rim, being narrow, and the dimensions of areas to be measured varying depending on the size of the tire. Therefore, because the size of an imaging unit that can be inserted into the space on the tire inner side is limited, and the tire inner side curves greatly in the tire width direction, it is necessary to divide the tire inner surface into two side inner surfaces and a tread inner surface in order to image the overall tire inner surface with the above-described conventional devices or methods. For example, it is necessary to image one side inner surface of the tire, the other side inner surface, and the tread inner surface separately, or to image both of the side inner surfaces of the tire and the tread inner surface separately. As a result, the man-hours involved in the imaging increase, and it takes time to image a single tire inner surface.